(CNN) -- Investigators identified a 22-year-old as the gunman responsible for shooting three people -- two of them fatally -- at a mall in suburban Portland, Oregon.
Sheriff's investigators believe that Jacob Tyler Roberts acted alone in what they described as a "heinous, horrible, tragic crime."
There were no immediate answers to the questions the community of Happy Valley had after the Wednesday shooting at the Clackamas Town Center: Roberts' motive remained unknown, and there was no apparent connection between the shooter and his victims, officials said.
The man and woman who were fatally shot were Cindy Ann Yuille, 54, and Steven Mathew Forsyth, 45.
The gunman hastily moved through the Macy's at the mall and toward the food court, located on the second floor, where he opened fire, the sheriff's office said.
The shooter then went down a corridor and out a back hallway that led downstairs, where he is believed to have shot himself.
Roberts was wearing a load bearing vest -- which many confused for a bulletproof vest -- and was armed with a semi-automatic rifle.
The rifle jammed at one point, but started working again, the sheriff said.
The injured woman was identified as Kristina Shevchenko by officials at the Oregon Health and Science University Hospital. She remains in serious condition, the hospital said.
The families of the other victims, Yuille and Forsyth, provided brief comments through authorities, but asked for privacy as they mourn their loved ones.
Yuille was remembered as a "everybody's friend" who put others first.
Forsyth was the father of two children with a great sense of humor and a "zest" for life, his family said.
Mall patrons were paralyzed during the shooting, as shoppers had no clue where the gunman would fire next.
Entire swaths of Clackamas Town Center turned silent. The only sounds were the blasts from the man's rifle and the ensuing screams. Even the mall's Santa dropped to the ground.
"I thought I was going to die," mall employee David Moran said. "The gunshots were so loud, it was very scary. ... Kids were crying. Parents were crying, too."
Kira Rowland was holding her 6-month-old baby in Macy's when the shots rang out.
The gunman wore a hockey mask and jogged through Macy's wielding a rifle, a woman told CNN affiliate KOIN.
As some panicked customers bolted for the exits, others ducked under store counters or hid behind racks of clothing.
The suspect announced aloud that "I am the shooter" as he ran through Macy's, said witness and store employee Austin Patty.
The shooter carried a rifle "like you would see in a video game."
As the shooting started, Patty ran out of the store, warning everyone in his path that there was a shooter on the loose and ordering them out of the store.
The sheriff's office confirmed that a rifle and a mask were recovered from the scene.
Investigators are reviewing surveillance footage to get a better picture of what happened.
The Clackamas Town Center is located in Happy Valley, Oregon, a suburb of Portland.
Erin Quackenbush-Baker was in a vulnerable position -- in the middle of the mall at a kiosk with her grandmother and three young children.
"I felt like sitting ducks, where we were."
During a brief halt in the gunfire, a man helped rush the family into a nearby Sephora store. That's where Quackenbush-Baker and her children hid for an hour, "waiting to see if we were going to be shot or not."
As word spread that the shooter was moving from store to store, customers at Sears burst into tears, Christina Fisher told KOIN.
"We were told to stand in a group by the top of the escalators and stay away from the windows out of the aisle. ... We stood there for probably a good 20 minutes," she said. "All of the sudden, somebody came through with a radio, yelling, 'Get down!' "
As the melee unfolded, some customers watched television news reports about the shooting from inside the Sears entertainment center, Tylor Pedersen told affiliate KGW.
Antonio Charro spotted a wounded woman near a cell phone store and tried to help, but to no avail.
"She had apparently been shot in the chest, and I couldn't get her turned over to help her," said Charro, who had been shopping at the mall with his daughters. "There was no one around. She wasn't breathing."
Clackamas County Sheriff Craig Roberts said about 10,000 people were in the mall at the time.
No law enforcement officers fired any shots when they arrived, sheriff's Sgt. Adam Phillips said.
The 1.4 million-square-foot mall will remain closed Wednesday as investigators look for clues about the attack.
Rowland said she's grateful she got distracted while shopping and didn't venture farther into the mall.
"I think if I hadn't stopped to smell that perfume, that maybe me and my baby wouldn't be here today."